In the field of medical analyses, pathological conditions, defined as inflammatory, are ascertained by measuring the sedimentation rate of the corpuscular part of the blood, in particular of the erythrocytes, or red corpuscles. In particular, the erythrosedimentation rate represents a non-specific diagnostic test of inflammatory conditions.
The classical or reference method for measuring the sedimentation rate of the blood is the Westergren method.
In recent years, this test has been considerably improved, in particular in terms of execution time, as described, for example, in the patents in the name of Duic U.S. Pat. No. 5,827,746, Breda U.S. Pat. Nos. 6,632,679 and 7,005,107. These patents describe the application of a technique called “stop and flow”, which provides to stop the flow of blood under examination inside a capillary tube and to optically measure by means of photometry the speed of aggregation of the corpuscular part of the blood which thickens after it has been stopped.
This technique has allowed on the one hand to reduce the amount of blood needed from a few ml required by the Westergren method to a few hundred micron required by the Breda method, and on the other hand to obtain the results of the measurement in only 20 seconds compared to the sedimentation in the Westergren method, which requires at least one hour's wait.
From document WO2004032702 in the name of Huscher, it is also known to use, instead of an optical/photometric detection, a detection with sound waves which are transmitted toward the tube where the sample to be examined is in transit, and are detected from the opposite side.
It is also known in the state of the art, in particular from WO2005022125, to integrate an apparatus to measure the sedimentation rate with a globule counter device, using the innovative technique of photometric measuring of the sedimentation rate in a capillary, the reduced performance times connected therewith and the low quantities of blood used.
A further improvement was given by WO2007006791, in which the use of particular substances called lactics was proposed, in order to obtain an optimal calibration and setting of the measuring instrument of the erythrosedimentation rate of blood.
Another evolution was shown in WO2007128684 which proposed the use of results obtained with the measuring of the erythro sedimentation rate in order to obtain information regarding a possible anemic condition of the patient.
In all the methods indicated above, which also use different measuring systems, the blood taken from the patients, even in very limited amounts, is introduced into tubular containers and subsequently the necessary measurements are carried out on the blood samples in transit.
One of the problems complained of in this type of optical/photometric measuring but also with other types of radiations, for example sound waves, is that the small Teflon tube normally used has a thickness which can generate an effect of deviating the incident ray with respect to the receiving device.
Moreover, a normal Teflon tube can have, in its manufacturing by extrusion, differences in thickness and section precisely in correspondence to the point where it is hit by the incident ray. Such differences in thickness and section of the Teflon tube, if they are at the point where the emitter creates deflections of the ray passing through, generate a disturbance and a non-linear reading which makes it difficult to calibrate the detection system so as to obtain repeatable instruments in the production stage.
Since the surfaces of the tube are not perpendicular to the incident radiations and have a refraction index that is different from the mean (air) in which the incident radiation is emitted and received, the surfaces of the capillary act as a lens, altering the geometry of the front of the incident wave.
The attached drawings 1a and 1b graphically show the situation of the state of the art, in which an emitter 100 emits a radiation 101 toward a Teflon tube 102 and on the opposite side there is a receiver 103 which detects the radiation after it has passed through the sample to be examined (not shown) present inside the Teflon tube 102.
As can be seen in FIG. 1a, the waves 101 are deflected four times as they pass through the thickness of the Teflon tube 102, so that it does not guarantee the precision of the result of the measurement.
In FIG. 1b it can be seen how even a collimated central ray can be deflected as it passes through the Teflon tube 102, in particular when its section is particularly non-uniform on the circumference, as shown in an accentuated form in the drawing, because of the tolerances of coaxiality between internal and external diameter of the tube.
It has been found that it is practically impossible to produce industrially Teflon tubes guaranteed with a constant section for the whole of their length, because the process of manufacturing by extrusion is a known technical limit.
As we said, however much an incident radiation is collimated to strike the tube in its central part, often these variations in thickness, caused by the impossibility of obtaining a standardized precision during production, induce errors in the optical measuring, so that an instrument can give different readings from instrument to instrument.
This problem is partly resolved using tubes with a greater diameter than is necessary (and as a consequence samples with a greater volume) or by using diffusive materials/surfaces (for example Teflon with respect to electromagnetic radiations) which however, reduce the sensitivity of the instrument.
Another considerable problem complained of in the use of this measuring technology concerns the contamination of the reading chamber between successive measurements. Indeed, after every measurement, and after the analysis, the blood sample is discharged and a new blood sample is introduced into the measuring volume.
Given that the ESR measurement is a physical measurement of the characteristics of sedimentation by the red corpuscles, for this type of test it is important to be certain that in a continuous stream of samples, there is no contamination between one sample and the next at the measuring point of the test.
To avoid having to wash the measuring volume after the discharge, the residues of the sample already analyzed are discharged by the new blood sample to be analyzed, as the hydraulic path which the blood has to follow in order to avoid pollution is rather long, which increases the volume of blood to be used, as well as the performance times.
In relation to the problems identified above, one purpose of the present invention is to supply a method, and the corresponding apparatus, to determine the sedimentation rate of blood, as well as other parameters correlated thereto, which allow an extremely quick analysis, easy and very reliable and precise.
Another purpose is to avoid washing between sequential samples, so as to achieve a simplification in the flow of work applied to an automatic, semi-automatic or manual instrument.
Another purpose of the invention is to produce a compact and easily transportable apparatus, practical to use in any condition or environment, and also usable as a disposable instrument in a surgery or hospital, in the so-called POC (Points of Care) for example.
The Applicant has devised and embodied the present invention to obtain these purposes and also other advantages.